LepR-expressing cells are a critical population in periodontal healing post periodontitis.

Identification of promising seed cells plays a pivotal role in achieving tissue regeneration. This study demonstrated that LepR-expressing cells (LepR+ cells) are required for maintaining periodontal homeostasis at the adult stage. We further investigated how LepR+ cells behave in periodontal healing using a ligature-induced periodontitis (PD) and a self-healing murine model with LepRCre/+; R26RtdTomato/+ mice. Lineage tracing experiments revealed that the largely suppressed osteogenic ability of LepR+ cells results from periodontal inflammation. Periodontal defects were partially recovered when the ligature was removed, in which the osteogenic differentiation of LepR+ cell lineage was promoted and contributed to the newly formed alveolar bone. A cell ablation model established with LepRCre/+; R26RtdTomato/+; R26RDTA/+ mice further proved that LepR+ cells are an important cell source of newly formed alveolar bone. Expressions of ß-catenin and LEF1 in LepR+ cells were upregulated when the inflammatory stimuli were removed, which are consistent with the functional changes observed during periodontal healing. Furthermore, the conditional upregulation of WNT signaling or the application of sclerostin neutralized antibody promoted the osteogenic function of LepR+ cells. In contrast, the specific knockdown of ß-catenin in LepR+ human periodontal ligament cells with small interfering RNA caused arrested osteogenic function. Our findings identified the LepR+ cell lineage as a critical cell population for endogenous periodontal healing post PD, which is regulated by the WNT signaling pathway, making it a promising seed cell population in periodontal tissue regeneration.

Notopterol Inhibits the NF-κB Pathway and Activates the PI3K/Akt/Nrf2 Pathway in Periodontal Tissue.

Notopterol, an active component isolated from the traditional Chinese medicine Notopterygium incisum Ting ex H.T. Chang, exerts anti-inflammatory activity in rheumatoid arthritis. However, its roles in suppression of inflammatory insults and halting progression of tissue destruction in periodontitis remain elusive. In this study, we reveal that notopterol can inhibit osteoclastogenesis, thereby limiting alveolar bone loss in vivo. In vitro results demonstrated that notopterol administration inhibited synthesis of inflammatory mediators such as IL-1ß, IL-32, and IL-8 in LPS-stimulated human gingival fibroblasts. Mechanistically, notopterol inhibits activation of the NF-κB signaling pathway, which is considered a prototypical proinflammatory signaling pathway. RNA sequencing data revealed that notopterol activates the PI3K/protein kinase B (Akt)/NF-E2-related factor 2 (Nrf2) signaling pathway in LPS-stimulated human gingival fibroblasts, a phenomenon validated via Western blot assay. Additionally, notopterol treatment suppressed reactive oxygen species levels by upregulating the expression of antioxidant genes, including heme oxygenase 1 (HO-1), NAD(P)H quinone oxidoreductase 1 (NQO1), catalase (CAT), and glutathione reductase (GSR), indicating that notopterol confers protection against oxidative stress. Notably, inhibition of Akt activity by the potent inhibitor, MK-2206, partially attenuated both anti-inflammatory and antioxidant effects of notopterol. Collectively, these results raise the possibility that notopterol relieves periodontal inflammation by suppressing and activating the NF-κB and PI3K/AKT/Nrf2 signaling pathways in periodontal tissue, respectively, suggesting its potential as an efficacious treatment therapy for periodontitis.

Axin2-CreERT2 mediated knockout of bone morphogenetic protein receptor type 1A caused abnormal secondary dentine and altered cell fate of Axin2-expressing odontogenic cells.

AIM: Inducing odontogenic differentiation and tubular dentine formation is extremely important in dentine repair and tooth regeneration. Bone morphogenic proteins (BMPs) signalling plays a critical role in dentine development and tertiary dentine formation, whilst how BMPR1A-mediated signalling affects odontoblastic differentiation of Axin2-expressing (Axin2+ ) odontogenic cells and tubular dentine formation remains largely unknown. This study aims to reveal the cellular and molecular mechanisms involved in the formation of secondary dentine. METHODOLOGY: Axin2lacZ/+ mice harvested at post-natal 21 (P21) were used to map Axin2+ mesenchymal cells. Axin2CreERT2/+ ; R26RtdTomato/+ mice and Axin2CreERT2/+ ; R26RDTA/+ ; R26RtdTomato/+ mice were generated to observe the tempo-spatial distribution pattern of Axin2-lineage cells and the effect of ablation of Axin2+ cells on dentinogenesis, respectively. A loss-of-function model was established with Axin2CreERT2/+ ; Bmpr1afl/fl ; R26RtdTomato/+ (cKO) mice to study the role of BMP signalling in regulating Axin2+ cells. Micro-computed tomography, histologic and immunostainings, and other approaches were used to examine biological functions, including dentine formation, mineralization and cell differentiation in cKO mice. RESULTS: The results showed rich expression of Axin2 in odontoblasts at P21. Lineage tracing assay confirmed the wide distribution of Axin2 lineage cells in odontoblast layer and dental pulp during secondary dentine formation (P23 to P56), suggesting that Axin2+ cells are important cell source of primary odontoblasts. Ablation of Axin2+ cells (DTA mice) significantly impaired secondary dentine formation characterized with notably reduced dentine thickness (Mean of control: 54.11 µm, Mean of DTA: 27.79 µm, p = .0101). Furthermore, malformed osteo-dentine replaced the tubular secondary dentine in the absence of Bmpr1a with irregular cell morphology, abnormal cellular process formation and lack of cell-cell tight conjunction. Remarkably increased expression of osteogenic markers like Runx2 and DMP1 was detected, whilst DSP expression was observed in a dispersed manner, indicating an impaired odontogenic cell fate and failure in producing tubular dentine in cKO mice. CONCLUSIONS: Axin2+ cells are a critical population of primary odontoblasts which contribute to tubular secondary dentine formation, and BMP signalling pathway plays a vital role in maintaining the odontogenic fate of Axin2+ cells.

Effect of lipoxin A4 on the osteogenic differentiation of periodontal ligament stem cells under lipopolysaccharide-induced inflammatory conditions.

Lipoxin A4 (LXA4) has been identified as the braking signal of inflammation, but the specific role of LXA4 in regulating the regenerative potential of periodontal ligament stem cells (PDLSCs) remains unclear. The aim of this study was to investigate whether and, if so, how LXA4 improves the osteogenic differentiation of PDLSCs in a lipopolysaccharide (LPS)-induced inflammatory environment. We detected the effects of LXA4 on the osteogenic differentiation of PDLSCs in vitro and explored the bone regenerative potential of LXA4-treated inflammatory PDLSCs in vivo using a calvarial critical sized defect model in male rats. RNA sequencing, real-time PCR and western blot were performed to elucidate the relevant potential mechanisms. Results showed that LXA4 promoted the proliferation, migration and osteogenic differentiation of PDLSCs in vitro, and effectively improved the impaired osteogenic capacity of PDLSCs induced by LPS both in vitro and in vivo. Mechanistically, LXA4 significantly promoted the PI3K/AKT phosphorylation under inflammatory conditions. Additionally, LY294002 (a PI3K inhibitor) blocked the effect of LXA4, suggesting that the PI3K/AKT pathway is a key signaling pathway that mediates the effect of LXA4 on the osteogenesis of inflammatory PDLSCs. These findings indicate LXA4 may be a promising strategy for periodontal regeneration using inflammatory PDLSCs.

Loss of ß-catenin causes cementum hypoplasia by hampering cementogenic differentiation of Axin2-expressing cells.

BACKGROUND AND OBJECTIVE: Although cementum plays an essential role in tooth attachment and adaptation to occlusal force, the regulatory mechanisms of cementogenesis remain largely unknown. We have previously reported that Axin2-expressing (Axin2+ ) mesenchymal cells in periodontal ligament (PDL) are the main cell source for cementum growth, and constitutive activation of Wnt/ß-catenin signaling in Axin2+ cells results in hypercementosis. Therefore, the aim of the present study was to further evaluate the effects of ß-catenin deletion in Axin2+ cells on cementogenesis. MATERIALS AND METHODS: We generated triple transgenic mice to conditionally delete ß-catenin in Axin2-lineage cells by crossing Axin2CreERT2/+ ; R26RtdTomato/+ mice with ß-cateninflox/flox mice. Multiple approaches, including X-ray analysis, micro-CT, histological stainings, and immunostaining assays, were used to analyze cementum phenotypes and molecular mechanisms. RESULTS: Our data revealed that loss of ß-catenin in Axin2+ cells led to a cementum hypoplasia phenotype characterized by a sharp reduction in the formation of both acellular and cellular cementum. Mechanistically, we found that conditional removal of ß-catenin in Axin2+ cells severely impaired the secretion of cementum matrix proteins, for example, bone sialoprotein (BSP), dentin matrix protein 1 (DMP1) and osteopontin (OPN), and markedly inhibited the differentiation of Axin2+ mesenchymal cells into osterix+ cementoblasts. CONCLUSIONS: Our findings confirm the vital role of Axin2+ mesenchymal PDL cells in cementum growth and demonstrate that Wnt/ß-catenin signaling shows a positive correlation with cementogenic differentiation of Axin2+ cells.

Activation of Wnt signaling in Axin2+ cells leads to osteodentin formation and cementum overgrowth.

OBJECTIVES: In this study, we used the mouse incisor model to investigate the regulatory mechanisms of Wnt/ß-catenin signaling on Axin2+ cells in tooth development. MATERIALS AND METHODS: Axin2lacZ/+ reporter mice were used to define the expression pattern of Axin2 in mouse incisors. We traced the fate of Axin2+ cells from postnatal Day 21 (P21) to P56 using Axin2CreERT2/+ and R26RtdTomato/+ reporter mice. For constitutive activation of Wnt signaling, Axin2CreERT2/+ , ß-cateninflox(Ex3)/+ , and R26RtdTomato/+ (CA-ß-cat) mice were generated to investigate the gain of function (GOF) of ß-catenin in mouse incisor growth. RESULTS: The X-gal staining of Axin2lacZ/+ reporter mice and lineage tracing showed that Axin2 was widely expressed in dental mesenchyme of mouse incisors, and Axin2+ cells were essential cell sources for odontoblasts, pulp cells, and periodontal ligament cells. The constitutive activation of Wnt signaling in Axin2+ cells resulted in the formation of osteodentin featured with increased DMP1 and dispersed DSP expression and overgrowth of cementum. CONCLUSION: Wnt signaling plays a key role in the differentiation and maturation of Axin2+ cells in mouse incisors.

[Research progress in the relationship between Veillonella and oral diseases].

Veillonella species, known as the early colonizer of oral biofilm, are prevalent in oral microbiota. Seven Veillonella species have been isolated from oral cavity. Their distribution varies not only with different people but also with different sites in the oral cavity. Oral Veillonella are associated with oral diseases. They contribute to the adhesion of Streptococcus mutans and consume the lactate generated by streptococci. Veillonella species play an important role in the occurrence and development of periodontal diseases by providing adhesion sites for Porphyromonas gingivalis and boosting immune responses. The production of lipopolysaccharide and H2S is related to other oral diseases, such as pulpitis, periapical periodontitis, and halitosis. Several studies have been conducted on the relationship between Veillonella and oral diseases and the interaction between Veillonella and other pathological microorganisms, but limited knowledge is available at the molecular level. This article reviews the research progress in the relationship between Veillonella and oral infectious diseases, such as dental caries and periodontal diseases.

[Advances in oral bacteria influencing host epigenetic regulation].

Epigenetics refers to a steady change in the level of gene expression caused by non-DNA sequence changes. Microbes can modulate host inflammation through epigenetic pathways to evade or expend immune responses. As an important part of human microbes, oral bacteria also have various epigenetic regulation mechanisms to affect host inflammatory responses. This article reviews the common pathways of epigenetic regulation in microbe infection and the regulation of host epigenetics by using oral microbes to provide a reference for the study of epigenetic-related mechanisms in oral diseases.

Mechanism of miR-148b inhibiting cell proliferation and migration of Schwann cells by regulating CALR.

The aim of this study is to investigate the effect of miR-148b on cell proliferation and migration of Schwann cells and explore its mechanism. The miR-148b group, miR-con group and the anti-miR-148b group, anti-miR-con group, si-con group, si-CALR group, Ctrl group, CALR group were transfected into Schwann cells by liposome method; the expression of miR-148b was detected by qRT-PCR; the cell viability was detected by MTT assay; the migration of cells was detected by Transwell method; WB assay was used to detect the protein expression of CALR. Firstly, we found that compared with miR-con group and si-con group, the proliferation and migration of miR-148b group and si-CALR group were significantly down-regulated (P < .05). Moreover, compared with anti-miR-con group and Ctrl group, anti-miR-148b group and CALR group cells proliferation and migration were significantly up-regulated (P < .05). In addition, miR-148b was targeted to CALR, and silencing CALR could reverse the inhibitory effect of miR-148b on Schwann cell proliferation and migration. In conclusion, miR-148b can regulate the proliferation and migration of Schwann cells. The mechanism may be related to the targeted negative regulation of CALR, which will provide a basis for targeted therapy of peripheral nerve injury.

Meat quality and cooking attributes of thawed pork with different low field NMR T(21).

A relationship of low field NMR T(2) components to meat quality and cooking attributes of pork was investigated. Longissimus muscle was removed from 23 pig carcasses at 24h postmortem for meat quality measurements and cooking test. Frozen samples were classified into three groups by LF-NMR T(21) of thawed samples: A (<40ms), B (40-44ms) and C (>44ms). There were significant differences (P<0.05) in pH, lightness (L* value) and pressing loss among the three groups. Cooking time to attain 70°C was slightly lower in group C than the other groups. Shear force value of cooked samples was not affected by T(21). The component T(21) correlated (P<0.05) with L* value, muscle pH and pressing loss, while L* value correlated (P<0.05) with thawing loss and muscle pH. Therefore, combined LF-NMR and color measurements could be a good way to differentiate water holding capacity of pork.